This chart works best with data that has equally distributed x values. For example, data sets with a data point per year.

To handle showing thousands of data points, Fusion Tables automatically buckets the data and identifies a value to represent each bucket, creating a representative line at any zoom level. As you zoom all the way in, the raw data appears as discrete points on the plot.

Roll over a point to see the average value, and the range of values that define the top and bottom of the bucket.

The top right corner indicates how much data is included in the current zoom range. For example, "Data aggregated from 10233 rows."

Example: Dow Jones

Here's an example using the Dow Jones Industrial Average over the past 100 years: